The objective of the proposed study is to reveal the changes in brain amine metabolism, especially dopamine, norepinephrine and serotonin as well as the enzymes L-dopa decarboxylase and glutamic acid decarboxylase in the striatum and other brain regions of monkeys made "dyskinetic" by L-dopa or chronic administration of high doses of neuroleptics such as chlorpromazine or haloperidol. In the case of the L-dopa treated monkeys, the accumulation and regional distribution of dopa and 3-O-methyl-dopa, one of its major metabolites, will be studied. The methods used will include a) Extraction and separation of L- dopa, 3-O-methyl-dopa, dopamine norepinephrine and metabolites (homovanillic acid) by a combination of the Dowex ion exchange method and alumina oxide extraction procedure. b) Extraction and separation of serotonin and 5-hydroxyindoleacetic acid by a modified organic solvent (butanol) extraction procedure. c) Fluorimetric determination of all above compounds. d) Radioisotope assay of L-dopa decarboxylase, L- glutamic acid decarboxylase (and later L-tyrosine hydroxylase) activities. The proposed study, in conjunction with the neurological, behavioural and pathological (morphological) studies, is expected to shed light on the neurochemistry of dyskinesias produced by chronic administration of chlorpromazine and other neuroleptics in psychiatric patients as well as by L-dopa in patients with Parkinson's disease.